<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>DOM</title>
</head>
<body>
	<id class="intro">hhhhhh</id>

	<div class="main">
		<p>bbbabablalalalal</p>
	</div>

	<div class="content">123</div>


	<script>
		
		var intro = document.getElementById('intro');

		var main = document.getElementById('main');

		var p = document.getElementsTagName('p')[0];

		var center1 = document.getElementsClassName('center')[0];


	</script>
</body>
</html>